Antibody-Drug-Conjugates (ADC's) which are useful for the treatment of cancer and other diseases are commonly composed of three distinct elements: a cell-binding agent; a linker; and a cytotoxic agent. The conventional method of conjugating a cell-binding agent, such as an antibody, to a cytotoxic agent, employs two distinct reaction steps with the antibody. In the first reaction step (the modification step), the antibody is reacted with a heterobifunctional linker to produce a linker-modified antibody. The modified antibody product is then optionally purified from the excess linker or hydrolyzed linker reagent. In the second reaction step (the conjugation step), the linker-modified antibody is reacted with the cytotoxic agent containing a reactive group, such as thiol, to generate the antibody-cytotoxic agent conjugate, which is again purified in an additional purification step.
The processes that have been previously described for manufacture of the antibody-cytotoxic agent conjugates are complex because they are encumbered with steps that are cumbersome to perform or produce immunoconjugates that are less pure or less stable than optimally desired. Thus, it would be desirable to modify or eliminate one or more manufacturing steps while improving the product quality, such as purity and/or stability.
In view of the foregoing, there is a need in the art to develop improved processes for preparing cell-binding agent-cytotoxic agent conjugates that are of substantially high purity and can be prepared avoiding cumbersome steps and by reducing time and cost to the user. The invention provides such a process. These and other advantages of the invention, as well as additional inventive features, will be apparent from the description of the invention provided herein.